Hyde J E, Walker I O
Biochim Biophys Acta. 1977 Feb 22;490(2):267-71.
The possibility has been investigated of selectively spin-labelling the cysteine residues of histone H3 in chromatin and probing by ESR conformational changes affecting the labelled area as the molecular environment is altered. About 90% of bound labels are attached to the thiol groups and are strongly immobilized in deep crevices. The remaining labels are bound to amino groups mainly on histone H1, giving rise to a more mobile component in the chromatin spectrum. No conformational changes involving the labelled cysteins could be detected as the histones were dissociated stepwise from the complex by NaCl, but treatment with urea led to a cooperative increase in mobility, indicating that the hydrophobic region around the cysteine residues is folded in a compact tertiary structure to which histone H4 may be bound in the native complex, but which is not affected by dissociation of the H3-H4 unit from the DNA. In addition, chymotryptic disruption of the chromatin has been followed and an estimate made from the rotational correlation times of the size and origin of the digestion fragment carrying spin-labelled cysteine 110.
人们已经研究了对染色质中组蛋白H3的半胱氨酸残基进行选择性自旋标记，并通过电子自旋共振（ESR）探测随着分子环境改变影响标记区域的构象变化的可能性。约90%的结合标记附着在巯基上，并强烈固定在深裂缝中。其余标记主要与组蛋白H1上的氨基结合，在染色质光谱中产生一个更易移动的组分。当通过NaCl使组蛋白从复合物中逐步解离时，未检测到涉及标记半胱氨酸的构象变化，但用尿素处理导致迁移率协同增加，这表明半胱氨酸残基周围的疏水区域折叠成紧密的三级结构，在天然复合物中组蛋白H4可能与之结合，但该结构不受H3 - H4单元与DNA解离的影响。此外，还追踪了染色质的胰凝乳蛋白酶消化过程，并根据携带自旋标记半胱氨酸110的消化片段的旋转相关时间对其大小和来源进行了估计。
